Validate jshint and add Travis CI support

<em>This pull is based on and includes #11 to avoid merge conflicts. Once #11 is merged, this will automatically appear as a single-commit pull.</em>

Moved all jshint options to the .jshintrc file.

This way editors with jshint-plugins pick it up, and we can also use node-jshint on the command line to lint all files at once.

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To use jshint locally: install nodejs and `npm install -g jshint`. Then run `jshint .` or `jshint [path or file]`.

See also: http://jshint.com/platforms/#text-editor-plugins

To make the Travis CI stuff work, you need to enable it in your account (only takes a few seconds):

http://about.travis-ci.org/docs/user/getting-started/#Step-one%3A-Sign-in